Remington M1903 stocks are very scarce while Remington 03A3 stocks can still be found w/o too much difficulty. You need to explain what a "navel" stock is in terms of design or markings because there's no discussion of these in any M1903 references. M1903s were used aboard various US Navy vessels, but there is no discussion of any sort of standardized US Navy markings.
A Rem M1903 stock might come up on Gunbroker or on Ebay, but its important to deal with a US source which is licensed for export otherwise the stock may be impounded by a zealous Homeland Security type who is monitoring the postal system.
Fake stock markings abound so it pays to be careful. M1903 and 03A3 stocks can be confused. The Bruce Canfield book on the M1903 has some good info on sorting them out.